# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc.  All rights reserved.
# https://developers.google.com/protocol-buffers/
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"""Provides a container for DescriptorProtos."""

__author__ = 'matthewtoia@google.com (Matt Toia)'

import warnings


class Error(Exception):
    pass


class DescriptorDatabaseConflictingDefinitionError(Error):
    """Raised when a proto is added with the same name & different descriptor."""


class DescriptorDatabase(object):
    """A container accepting FileDescriptorProtos and maps DescriptorProtos."""

    def __init__(self):
        self._file_desc_protos_by_file = {}
        self._file_desc_protos_by_symbol = {}

    def Add(self, file_desc_proto):
        """Adds the FileDescriptorProto and its types to this database.

        Args:
          file_desc_proto: The FileDescriptorProto to add.
        Raises:
          DescriptorDatabaseConflictingDefinitionError: if an attempt is made to
            add a proto with the same name but different definition than an
            existing proto in the database.
        """
        proto_name = file_desc_proto.name
        if proto_name not in self._file_desc_protos_by_file:
            self._file_desc_protos_by_file[proto_name] = file_desc_proto
        elif self._file_desc_protos_by_file[proto_name] != file_desc_proto:
            raise DescriptorDatabaseConflictingDefinitionError(
                '%s already added, but with different descriptor.' % proto_name)
        else:
            return

        # Add all the top-level descriptors to the index.
        package = file_desc_proto.package
        for message in file_desc_proto.message_type:
            for name in _ExtractSymbols(message, package):
                self._AddSymbol(name, file_desc_proto)
        for enum in file_desc_proto.enum_type:
            self._AddSymbol(('.'.join((package, enum.name))), file_desc_proto)
            for enum_value in enum.value:
                self._file_desc_protos_by_symbol[
                    '.'.join((package, enum_value.name))] = file_desc_proto
        for extension in file_desc_proto.extension:
            self._AddSymbol(('.'.join((package, extension.name))), file_desc_proto)
        for service in file_desc_proto.service:
            self._AddSymbol(('.'.join((package, service.name))), file_desc_proto)

    def FindFileByName(self, name):
        """Finds the file descriptor proto by file name.

        Typically the file name is a relative path ending to a .proto file. The
        proto with the given name will have to have been added to this database
        using the Add method or else an error will be raised.

        Args:
          name: The file name to find.

        Returns:
          The file descriptor proto matching the name.

        Raises:
          KeyError if no file by the given name was added.
        """

        return self._file_desc_protos_by_file[name]

    def FindFileContainingSymbol(self, symbol):
        """Finds the file descriptor proto containing the specified symbol.

        The symbol should be a fully qualified name including the file descriptor's
        package and any containing messages. Some examples:

        'some.package.name.Message'
        'some.package.name.Message.NestedEnum'
        'some.package.name.Message.some_field'

        The file descriptor proto containing the specified symbol must be added to
        this database using the Add method or else an error will be raised.

        Args:
          symbol: The fully qualified symbol name.

        Returns:
          The file descriptor proto containing the symbol.

        Raises:
          KeyError if no file contains the specified symbol.
        """
        try:
            return self._file_desc_protos_by_symbol[symbol]
        except KeyError:
            # Fields, enum values, and nested extensions are not in
            # _file_desc_protos_by_symbol. Try to find the top level
            # descriptor. Non-existent nested symbol under a valid top level
            # descriptor can also be found. The behavior is the same with
            # protobuf C++.
            top_level, _, _ = symbol.rpartition('.')
            try:
                return self._file_desc_protos_by_symbol[top_level]
            except KeyError:
                # Raise the original symbol as a KeyError for better diagnostics.
                raise KeyError(symbol)

    def FindFileContainingExtension(self, extendee_name, extension_number):
        # TODO(jieluo): implement this API.
        return None

    def FindAllExtensionNumbers(self, extendee_name):
        # TODO(jieluo): implement this API.
        return []

    def _AddSymbol(self, name, file_desc_proto):
        if name in self._file_desc_protos_by_symbol:
            warn_msg = ('Conflict register for file "' + file_desc_proto.name +
                        '": ' + name +
                        ' is already defined in file "' +
                        self._file_desc_protos_by_symbol[name].name + '"')
            warnings.warn(warn_msg, RuntimeWarning)
        self._file_desc_protos_by_symbol[name] = file_desc_proto


def _ExtractSymbols(desc_proto, package):
    """Pulls out all the symbols from a descriptor proto.

    Args:
      desc_proto: The proto to extract symbols from.
      package: The package containing the descriptor type.

    Yields:
      The fully qualified name found in the descriptor.
    """
    message_name = package + '.' + desc_proto.name if package else desc_proto.name
    yield message_name
    for nested_type in desc_proto.nested_type:
        for symbol in _ExtractSymbols(nested_type, message_name):
            yield symbol
    for enum_type in desc_proto.enum_type:
        yield '.'.join((message_name, enum_type.name))
